1) Field of the Invention
The present invention relates to novel quinolone derivatives and salts thereof, said derivatives and salts having excellent antibacterial activities, to preparation processes thereof and also to antibacterial agents containing the same.
2) Description of the Related Art
New quinolone agents having pyridonecarboxylic acid as a basic skeleton have excellent antibacterial activities and a broad antibacterial spectrum, so that they have attracted interests as synthetic antibacterial agents comparable with antibiotics. Among these, norfloxacin [Japanese Patent Application Laid-Open (Kokai) No. 141286/1978], enoxacin [Japanese Patent Application Laid-Open (Kokai) No. 31042/1980], ofloxacin [Japanese Patent Application Laid-Open (Kokai) No. 46986/1982], ciprofloxacin [Japanese Patent Application Laid-Open (Kokai) No. 76667/1983] and the like have already found wide-spread clinical utility as therapeutic agents for infectious diseases.
The new quinolone agents known to date are however not fully satisfactory either in antibacterial activities, oral absorption, long-acting property, side effects on central nervous system, etc. To solve these problems, investigations are now under way, especially on substituents on positions 1, 5, 6, 7 and 8 of the quinoline and naphthyridine skeletons.